Editado por Immense Potato: 5/10/2015 1:01:31 AMAgility increases your movement speed and jump height/distance. The +2 Agility ability essentially gives your character a little speed boost. And it takes effect when you have the gun in your hands. Not just equipped.
It mean that when the icebreaker or any other +2 agility weapon is i your hand and you can fire it. Thats when the perk works